Off-highway vehicles (“OHVs”), such as mining vehicles used to haul heavy payloads, typically employ motorized wheels for propelling or retarding the vehicle in an energy efficient manner. This efficiency is typically accomplished by employing a large horsepower diesel engine in conjunction with an alternator, a main traction inverter, and a pair of wheel drive assemblies housed within the rear tires of the vehicle. The diesel engine drives the alternator and the alternator, in turn, powers the main traction inverter thereby supplying electrical power having a controlled voltage and frequency to electric drive motors of the wheel drive assemblies. Each wheel drive assembly houses a planetary gear transmission that converts the rotation of the associated drive motor energy into a high torque, low speed rotational energy output which is supplied to the wheels.
Planetary gear transmissions are generally operated in a wet lubricated condition. As will be appreciated, it is generally desirable to minimize or prevent leakage of lubricants, e.g., oil, from wheel drive assemblies as such leakage leads to vehicle downtime for disassembly, inspection and repair.
In connection with the above, OHV wheel assemblies typically include a torque tube sealing arrangement that performs both torque transmission and sealing duties. In particular, typical wheel assemblies may include a torque tube to facilitate torque transfer to the wheels of the OHV, and a sealing component (referred to as an oil seal body or “flinger”) attached to the torque tube via friction or interference fit and a multitude of clamp plates, bolts, and washers. The torque tube is a generally cylindrical component manufactured from a welded fabrication of steel barrels having gear teeth at one end and a flange for bolting to a wheel hub at the other. These gear teeth mesh with a planetary gear system in the wheel to transmit torque from the gear system to the wheel hub. The tires of the OHV are mounted to the wheel hub and the transmission of torque through the torque tube into the wheel hub rotates the tires and, therefore, moves the OHV forward.
The flinger is a cylindrical steel component containing a number of axial grooves that creates a geometry resembling fingers. These fingers mesh with a similar but mirrored component that is mounted on the wheel motor's stationary frame that, together, form a sealing labyrinth for containing oil within the wheel assembly of the OHV.
During operation of OHVs employing this type of torque tube sealing arrangements, the planetary gear system that is transmitting power to the torque tube may contribute to a triangularization or deformation effect in the torque tube. This deformation of the torque tube may be conferred onto the flinger that is attached to it. In particular, because the flinger is not mechanically fixed to the torque tube in the theta direction, it relies purely upon the friction generated by the interference fit and the clamp plates, bolts, and washers to keep it rotating in time with the torque tube. However, the potential deformation of the torque tube has the effect of potentially manifesting a shear force in the flinger, causing it to rotate relative to the torque tube instead of with it. This may manifest a shear force in the seal body, however, causing it to rotate relative to the torque tube, rather than with it. This relative rotation is referred to as precession and can potentially, over time, adversely affect the interference fit between the torque tube and flinger, resulting in a gap between the surfaces sufficient for leakage of oil.
In view of the above, it is desirable to provide a torque tube sealing arrangement in which cyclic precession is reduced. It is also desirable to provide a torque tube sealing arrangement that is more robust and has fewer parts than existing torque transmission and sealing arrangements.